The Stack Overflow Podcast

From cryptography to consensus: Q&A with CTO David Schwartz on building blockchain apps

Episode Summary

On this sponsored episode of the podcast, we talk with Ripple CTO David Schwartz about the promise that decentralized trust and distributed consensus has for software development — and for more transparency in ownership.

Episode Notes

Right now, plenty of people are building businesses on social media platforms, on streaming platforms, and on market platforms that they don’t control. That platform can make the rules in any way they want and remove access at any time. That means founders are potentially one step away from losing their livelihood. The same goes for consumers buying from these platforms: if you lose access to your account, there goes all your purchases. As it turns out, you were licensing everything, not buying it. 

On this sponsored episode of the podcast, we talk with Ripple CTO David Schwartz about the promise that decentralized trust and distributed consensus has for software development — and for more transparency in ownership. 

Episode notes:

Cross-border payments, while they might not be the sexiest app, are one of the best product-market fits for blockchains

Learn more about Ripple at their home page

Check out the documentation to learn more about building on the XRP Ledger. 

Congrats to Lifeboat badge winner, asmeurer, for their answer to What does `S` signify in SymPy?


Episode Transcription

[intro music plays]

Ben Popper Hello, everybody. Welcome back to the Stack Overflow Podcast, a place to talk all things software and technology. I am your host, Ben Popper, Director of Content here at Stack Overflow, joined as I often am by my colleague and collaborator, Ryan Donovan. Hey, Ryan. 

Ryan Donovan Hi, Ben. How are you today? 

BP I'm doing well. So today we are going to be chatting with the folks from Ripple who are sponsoring this episode and I think it's going to be really interesting. We've had some folks from Ripple on the podcast before to talk about some of the use cases that they power, and it's been a super interesting couple of years in the world of Web3 and blockchain and crypto so we're excited to have David Schwartz, who is CTO over at Ripple, on the program today. Hi, David.

David Schwartz Hi, Ben. Hello, Ryan. I'm very excited to be here. 

BP So the first thing we always ask folks to do is just help us get situated a little bit. How did you get into the world of software and technology? 

DS It's kind of funny. I was always interested in technology as a kid. I would mess with all kinds of things like motion detectors that opened doors and just analyzing and trying to understand the world around me. My father was into computers. He was building computers out of relays which is pretty crazy. And it's funny, I decided the one thing I didn't want to do was write software, which is pretty funny considering that's pretty much what I did for most of my career. I thought I wanted to build physical networks. I guess my thinking was the satisfaction of building something physical, particularly something on a large scale, and then seeing it work was really what motivated me, and it took me a while to realize that that's what software developers do. The thing that I wanted that I thought was the reason I didn't want to get into software development, I had the logic completely backwards. There's no field where you can build something complicated and amazing more quickly and see it work on a larger scale than when you write software and deploy it to a live system. I got very addicted to this idea that there was something that we couldn't do and you could sit down at a computer and punch a couple buttons and then people could do it. And I have to say, since I became CTO I've been doing that less and frankly I really miss it. I understand that the way you scale is by getting other people to do things rather than doing them yourself and providing your expertise and knowledge to allow other people to work faster and build better, but it's not as intellectually satisfying for me. And so I have to keep telling myself that things I'm doing are important because I don't feel it on that sort of visceral level. 

BP Gotcha, gotcha. That makes sense. You have a super interesting history in, as you pointed out, bringing the first ISDN service to South Florida, so helping build out the internet at a time when that meant physically building it out, right? 

DS Yeah, it wasn't built out. I mean, it physically wasn't there yet. But I started to realize that the exciting stuff was there in the early days when no one had done it before, but after a while, let's be honest, someone described internet service providers as like the gas stations of the information superhighway. Not to disparage anybody who works there; they solve real complicated and interesting problems, especially on a high end, and they're innovating, but not in a way that is really as tangible to the customers. I mean, not in a way that's tangible to the users. We just see the internet as just something that just works, do you know what I mean? It's not visible. We kind of take it for granted and so it's just not as exciting to me as building things that enable people to have new capabilities they didn't have before.

BP So David, earlier on you mentioned that as early as 2011 you started working in the crypto space, but specifically on the actual sort of cryptographic side of things. I remember when the Bitcoin White Paper came out. For a while it just sort of went unnoticed. It was being shared on sort of obscure cryptography listservs and things like that. What was it that brought you to that world and what was some of the early stuff that you were working on or just kind of brought you into the world of blockchain? 

DS Well, it was kind of right place, right time for me. So I was working in the cryptography field before then. I was doing secure cloud storage and secure messaging for large enterprises and military customers. I was very interested in things that I wasn't able to do in that job that were important to me, things like sort of the democratization of the flow of information, and then the democratization of the flow of money was something that was very meaningful to me intellectually. And so I was in the right place at the right time. I discovered Bitcoin probably in about mid-2011. I actually used this website called StumbleUpon where you tell it what you're interested in and it tells you what you should be interested in. A lot of services do that for music; this sort of does that for information. And so I told it the things that I was interested in and it says, “Have you seen this thing,” and it’s what led me to the first Bitcoin forum. And who works in crypto who wouldn't be interested in a community whose guiding ethos is, “That's where all the money is, that's where the economy should be.” And the democratization and the sort of libertarian aspects of it were immediately important to me– not as radically so as others, but I immediately found this just very interesting. 

RD So we've all seen the news. Bitcoin and all the crypto and NFTs, they all had kind of a turbulent year, but you've been there since the beginning and you built blockchains. So do you think there's going to be a rich future for these Web3 techs? 

DS I mean, I certainly hope so. I'm not discouraged by the sort of boom and bust cycle. Everybody's first one is that you think that it's going to be over, but how many times was the death of the internet predicted? How many times has the death of Bitcoin been predicted and other things? There are a lot of bad actors in the space. It's true. There's a lot of scams. There's a lot of things that just don't make any sense. And some of it is just that we don't know what the right answers are yet. It's a plus and it's a minus. If you build something, it could turn out not to be the right thing and you could build something that turns out not to get traction. But on the other hand, people are exploring in many, many different directions, and we don't know what the right ones are yet. It's very early, and so it's not unusual to have people get very excited about many different things that turn out to be bad ideas. Now, maybe because they're scammers, but maybe also because we didn't know it was a bad idea until we tried it. We saw this with the dotcom boom followed by a bust. We've seen many waves of AI booms, we're seeing one right now. 3D movies have gone through many boom and bust cycles. And to be fair, most things that people think are going to change the world don’t. But there are some reasons why I think this is different, and one of the big ones is that this resonates with sort of a real world pattern that's been going on for some time, which is sort of the flow of people who use the internet from passive consumers of information to creators of information to sort of curators and community manager participants to community managers and curators and then owners and I think this is sort of a continuum that's going to happen with or without Web3 technologies. And I think Web3 technologies are coming along at a time when they solve a problem that people actually have. And where these things tend to fail is when they don't solve problems that people actually have. Does 3D movies solve a problem that anybody actually has? No. It's kind of cool, and everybody who sees them for the first time thinks it's really cool, but it doesn't really solve a problem somebody actually has. So there are people who have built their entire lives and their presence on social media platforms, so they've built their businesses on social media platforms or streaming platforms or platforms of all kinds where if they lost their access to that platform or that platform's rules changed in ways that they didn't like, that would destroy their livelihood. They would have to start over from scratch. And these systems have their own aims. They have their own revenue models, they have their own goals and aspirations, and so you've seen people who've been kicked off a platform or have had a platform's rule change in ways that are disadvantageous to them and they lose a significant piece of what's important to them. So these technologies are coming along at a time when there is a real problem for them to solve. 

BP Yeah, that makes a lot of sense and I liked what you said about there being booms and busts in other areas. It's easy to get caught up in what's happening with AI now and be like, “Wow, this is brand new,” but of course this is the culmination of many cycles where these kinds of technologies were promising but not quite there. I remember reporting on chatbots in like 2015-2016. They were going to be the big thing and then they weren't quite good enough and kind of took a back seat and now here we are again. So I wanted to sort of dig in a little bit on utility, because I thought what you said was really interesting. In our earlier conversation with Ripple we chatted a little bit about what some of the key use cases are now. Can you just let listeners know what are some of the things right now that Ripple does, and where do you think sort of the future of the technology you're using could go when it comes to, for example, cross-border transactions, which was a really interesting conversation we had in the past?

DS You're one of the few people who probably describes cross-border payments as interesting. I usually get the reverse that it's so boring because all you can do is send a payment and receive a payment. If you're a developer you're like, “Oh, there's two things I can do. Cool. Once I’ve done those two things, that's three hours, then what do I do for the rest of my life?”

BP I guess what makes it cool to me is that I've known many people who, because of their status or immigration they're helping to take care of family back home, or they've migrated because of some issue and now they're a refugee, and the ability to send money around the world in a more frictionless and affordable way to me is really meaningful. I guess maybe the underlying technology is a bit simple, as you point out, but tell folks a little about how that works and maybe some of the other things in the stack that you're building. 

DS So yeah, payments are the trillion dollar elephant in the room. International payments particularly are terrible. There's a very good product market fit. It's not as seductive to developers, but it is a real problem that I think these technologies are going to solve and I think that there's tremendous opportunity to solve that problem, even if many people don't consider it as interesting, as the sizzling thing that they've heard about. Where that sizzle is right now are things like NFTs are really exciting people. I think a lot of people think that they're just looking at them in the collectible space, but I think NFTs are essentially embodiments of digital rights, and digital rights is another many tens of billion dollar industry. Everybody has bundles of digital rights, whether it's books, whether it's songs, whether it's video games, whether it's movies that they've paid for, and these systems are not great. If you buy a movie on a platform or on your cable company's platform, if you drop your service with them you lose all of the movies that you bought. All of the digital rights that you had, you lose. So these are systems that are not built around ownership. They're built around licensing, which is a completely different and less interesting concept. The other thing that's interesting to me is loans, and it's interesting to me for the opposite of the reason that it's interesting to most people. So most think about, “Hey, it'd be pretty cool if I could borrow money,” but I think about it the opposite way. I think it's pretty cool if you had good ways to lend money. As Americans, we have great access to tools that we can manage our money with but a lot of people in the world don't. They don't have access to basic financial services, and having some way to store their money in a secure platform where they could get some kind of return that made some kind of sense I think is extremely interesting. The United States started with landlines, everybody had landlines here and then we moved to mobile phones. But the rest of the world, or in a lot of countries that didn't bother building landlines, they were able to sort of skip steps. And I think especially in the money management of what you can do with your money and how you can hold it and how you can manage it, there are going to be countries that are going to skip steps. There's countries where all they have is basically one company that's PayPal-like and that's it. That's their financial infrastructure for individuals. So I think there's those kinds of opportunities in providing people ways to manage their money beyond just having it on a mobile payment platform where literally all you can do is send and receive.

BP Yeah, I remember as a reporter doing a story about M-PESA, which is one of the more popular sort of mobile carriers that lets you do a lot of banking. And as you point out, it was a great opportunity for consumers in some ways, but also had quickly become dominated by a single player which eventually can be a bad thing for the consumer.

DS That lack of consumer ownership is something that I think these technologies can really [leverage], where you're not at the mercy of one large player.

BP Right.

RD So what do you think the sort of killer app for blockchain will look like? What's the thing that's going to get sort of mainstream adoption? 

DS So I have to start by saying that I don't know. I think we're very early, and with many technologies, if you asked me what people would use internet bandwidth for 15 years ago I would never have said that everybody can watch a different cat video. If you had asked me what people would use email for, look at your email today. 99% of your email messages wouldn't have existed 10 years ago. There's no way someone back then could have foreseen the way people would use email, so it's early. And there's a reason why I think payments are so important, which is globalization. There've been two huge waves of globalization that have radically changed the economy. One of them was the physical delivery of goods. Things like the shipping container– the fact that you could get something from overseas and it could go from a plane to a truck to a ship to you without having to be constantly repacked and relabeled, that was a massive revolutionary improvement in the economy. And then of course the internet. It does no good if a physical good can get from a factory in China to my desk if I don't know who's making what and I can't place an order. But the payment is the missing piece that's that missing leg of the stool. So payments, again, not so sexy for many people, but that's one that I think is critical. And I think the other one is just management of money. In the United States we're very spoiled. We’re overbanked. We have so many places that we can store and manage our money. We have such easy access to investments. That's not the case in most of the rest of the world, particularly in developing countries, and so I think there's this tremendous opportunity to give people better ways to hold money. And I think the last one really is decentralized ownership where you don't build your presence in somebody else's world, in a world that somebody else owns and controls, where what's yours is not yours because somebody else is sort of allowing you to access it. Because people's online presence is becoming more and more valuable and important to them, whether it's your personal presence on a social media company, whether it's the network and community that you've built for your business, and having ownership and control over that and having portability so if you don't like a particular platform you can take that to some other platform, those capabilities I think are going to be very big. And I think what's going to happen is the existing companies are going to have to push back. They're going to have to offer those types of technologies if they want to stay competitive. So we're going to have this interesting world, it's going to be an exciting space in Web2 as well as Web3. If you want to be on the Web2 side, they're going to have to compete with Web3. They're not going to go down without a fight and the fight won't necessarily be adopting Web3 technologies. So it's going to be interesting on the Web2 side as they sort of compete, but I think on the Web3 side it's going to be exciting as they try to offer this sort of evolution from where the community is the product, but where your management of the community is part of your experience. 

BP Do you think that'll come from the bottom up or the top down? I feel like I see content creators now clearly understand that they need to diversify their platform portfolio, so they'll have an Instagram, a TikTok, a Twitter, they'll be on YouTube, and then they'll have their own website, and they'll have a Patreon which is direct to fans, and that's a connection they control in a stronger way. And then often people who have online personalities will start having live events. They'll take it off the internet and that's another way to do it. But who gets to make that demand, or who gets to break that barrier where they say, “Listen, I need my digital identity and ownership and persona to be portable. When I come to these different platforms, I want to come as me, this version of myself on the blockchain, and here's what I own and these are my rates.” Is that something that the Mr. Beast’s of the world are going to do? Or is that something that is going to come from the bottom up with a lot of people creating new, more federated systems like a Mastodon and then other people sort of follow along?

DS I think you're always going to see both. I think if you look at prior revolutions, people forget that the internet revolution started out with the military and large research institutions and then it reached a point where it was attractive to people who didn't have specific needs and then they sort of meet in the middle. I think you're going to see both approaches and I think it's hard to know. But I think as you point out, we're already seeing some of the bottom-up type stuff where people are saying, “I don't want to put all my eggs in one basket.” There's a long time where bottom-up approaches can be very successful where community-driven approaches, and I'm sure you've heard of some of the decentralized competitors to social media products and to streaming platforms that have been tried, and those projects have not been all that successful, but I think there's room for them to innovate and there's room for them to be very successful. But ultimately I do think, unfortunately at one time I believed the opposite, but I think if you look at the pattern of the internet, you had this middle time period where the internet was very democratic and now you have new gatekeepers that have emerged. So I would like to think Web3 will be different, but I think you may have that same pattern where you have this time period where it's very experimental, it's very innovative, and there's all these small projects and some of them can be wildly successful, and then eventually people will congregate around the solutions that work best. But on the bright side, we have probably 10 years while everything seems interesting and where there's plenty of room for success with all different types of technologies. 

RD So it sounds like there's a whole lot of greenfield to play in here. How does somebody who's interested in this start building on the blockchain? What skills do you need?

DS So first I would say learning blockchain basics. You're never going to go wrong with learning as much as you possibly can about the basics. Who are the big players? What are the different technologies? The crypto side of it– how do these technologies work? What makes them different? And then the next thing I would say is work around what you already know. Don't try to start in the middle of nowhere. If you're a user interface developer, well, blockchain projects need user interfaces. If you like to write the guts of something, well, smart contracts are the guts of what's going on in the Web3 space. So I would say, if you know JavaScript, almost everything needs JavaScript, so that's a good place. But if you're very strong in some other language, that's perfectly fine. A lot of these projects can be done in whatever technologies are interesting to you. I would say start with things that are adjacent to what you already know and don't try to start all over somewhere else if you're already in the space. 

RD If somebody wants to sort of do the ‘hello world’ of building on the blockchain, what's a project that they can do? 

DS So probably you can start with almost any of the blockchains. You can build those kind of simple projects. Obviously, as someone who was very involved in the development of the XRP Ledger, I would love to see people learning the features of the XRP Ledger and looking at some of the capabilities there, mostly around payments which I know is not super sexy, but there's all kinds of really nice features in there around asset exchange and asset management which is really nice. Also a lot of people are developing on the Ethereum Virtual Machine with tools like Solidity, Rust, again, there's a lot of projects built around Rust. You can develop smart contracts in Rust. I mean, it's hard to pick something just because there's so many options. Again, I would say focus on the skill set that you have. Focus on the thing that's adjacent to the skills that you have, rather than trying to jump into the middle of nowhere.

BP And from your perspective, you mentioned how you started in hardware then learned that you love software and now as a CTO still kind of wish you could get your hands dirty every once in a while. Are there things you're working on either as part of your day-to-day at your job or privately that you're excited about? Do you have side projects in the world of Web3? 

DS I was incredibly excited about the work I did on the automated market maker for the XRP Ledger because one of the things that people perceive as a big downside of cryptocurrencies is their volatility, and an automated market maker is sort of an engine that turns volatility into yield. So that was just incredibly fun to me because I spent a lot of time analyzing things like Forex markets and trading, so that just played to the things that I find the most intellectually interesting. There’s also work on adding a much more powerful smart contracts layer to the XRP Ledger called hooks. I'm more of an observer on that, but I mean, super exciting. But yeah, one of the downsides of my current role as CTO, one of the things that is a little sad for me is that I don't get to get my hands as dirty as I used to. I'm busy helping other people be able to build things and so I don't get as much time to build stuff for myself. It's a little sad. 

BP Gotcha. Well, someday you can step back to IC. We've done a few podcasts so you can finish up and then you can get back in the trenches if you feel like it. 

DS I did work on optimizing some XRP Ledger code. Someone pointed out that there was some code that was showing up in their performance analysis and so I'm like, “Oh, this is interesting! Let me just optimize this little piece of code.” And it was just a small, quick job but I have to say it was just very satisfying in a way that management isn't.

[music plays]

BP All right, everybody. It is that time of the show. We want to say thanks so much for listening. As we do at the end of every episode, we're going to shout out someone who came on Stack Overflow and help spread a little knowledge. A Lifeboat Badge was awarded to asmeurer, “What does the ‘S’ signify in Sympy?” Well, we have the answer for you and a lifeboat badge for saving that question, so appreciate it. I am Ben Popper, the Director of Content here at Stack Overflow. You can always find me on Twitter @BenPopper. You can send us questions or suggestions for the show: And if you like what you hear, why don't you leave us a rating and a review. It really helps.

RD I'm Ryan Donovan. I edit the blog here at Stack Overflow. It can be neatly located at And you can find me on Twitter @RThorDonovan. 

DS My name's David Schwartz, I'm CTO at Ripple. You can find me on Twitter at @JoelKatz, and check out Ripple at or the XRP Ledger at

BP All right, everybody. Thanks for listening. We will talk to you soon.

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